1. Field of Invention
The invention relates generally to the aerospace industry, and more particularly to the launching of payloads into orbit around the earth. In particular, the invention relates to a launch vehicle and a method of launch vehicle operation for deploying a satellite into a predetermined orbital path around the earth.
2. Description of the Related Art
Launch vehicles for delivering payloads such as satellites into earth orbit have become increasingly important as the communications industry has increased its reliance upon satellite-based communication systems. As a result of this increased reliance on satellite-based communication systems, a variety of launch vehicles have been implemented in an effort to deliver satellites into earth orbit. However, these launch vehicles have not proven to be entirely satisfactory for reasons of reliability, cost of manufacture, and the availability of necessary components. It is for all these reasons that the launch vehicle and method of launch vehicle operation of the present invention were developed.
The design and operation of a launch vehicle is, to a large extent, dictated by the size of the payload to be carried and the orbit to which the payload is to be delivered, the location of the launch site, and the cost and availability of parts for constructing the launch vehicle. Early satellite launch vehicles employed a "series" stage configuration in which a number of successively-ignitable rocket stages were stacked one on top of another. The term "rocket stage" as used throughout this disclosure refers to the discrete, simultaneous firing and operation as a group of one or more rocket motors until engine shut-down. In series configured launch vehicles, a prior, burn-out stage is jettisoned from the launch vehicle, usually with the aid of pyrotechnic devices such as explosive bolts, prior to ignition of a successive stage.
Early preference for the series stage configuration for launching commercial payloads such as satellites stems to a large extent from the familiarity of launch vehicle frameworkers and designers with series stage configurations resulting from work on predominantly military-oriented launch projects. However, the design criteria for a military project, which tend to dictate a series stage configuration, influence the design of a commercial launch vehicle to a much lesser extent. For example, design parameters such as maximum vehicle width, which are of considerable importance for military projects involving launchings from subterranean launch sites such as missile silos, are less critical for commercial launch vehicles. Additionally, there is less of a need in a commercial context to skew in a direction of absolute performance the relative equilibrium between performance and cost of manufacture. Instead, the balance in a commercial context is directed more toward the side of cost-effectiveness of the launch procedure and the launch apparatus. For these reasons, parallel rather than series rocket engine configurations have gained increasing acceptance.
In a parallel rocket engine configuration, two or more rockets are placed in a side-by-side (rather than vertical) configuration, resulting in a launch vehicle which is generally wider, but shorter in height, than is a series configuration of similar propulsive capabilities. The parallel configuration is particularly advantageous in a commercial context because it provides for a greater degree of payload flexibility by allowing for a relatively wide range of payloads by simply changing the number of "strap-on" rocket motors assembled to a central or core stage of the launch vehicle. The generally shorter, wider configuration of the parallel arrangement of rocket motors also results in a launch vehicle which exhibits a considerable degree of both static and dynamic stability over its series counterpart. A further advantage is provided by the near collocation of the vehicle center of gravity and its thrust and aerodynamic centers. As a result of this near collocation of center points, the parallel configuration rockets tend to be more readily controllable, even in the absence of external fin augmentation.
In spite of the seemingly great operational advantages afforded by a parallel rocket configuration over its series counterpart, serious operational and cost deficiencies nevertheless exist with current parallel configuration launch vehicles. For example, one known parallel configuration launch vehicle employs as its first stage a pair of specially designed and constructed solid fuel rocket motors which carry the launch vehicle beyond the earth's sensible atmosphere before the second stage is ignited. While this rocket affords a tremendous payload capacity of on the order of 40,000 lbs. for deployment into a low earth orbit of generally no more than 300 nautical miles for a range of orbital inclinations, it is not well suited for transporting considerably smaller payloads such as small to medium-sized communication satellites, which typically range in weight from about 150 lbs. to about 3,500 lbs., for deployment at lower polar earth orbits, typically from about 100 nautical miles to about a 450 nautical miles above the earth's surface. As used throughout this disclosure, the term "polar orbit" is meant to refer to an orbital path around the earth that is inclined with respect to the earth's equator at an angle of about 90.degree.. This known launch vehicle is therefore quite limited in the range of payload weights it can efficiently deliver into earth orbit, as it was designed specifically for transporting relatively heavy, bulky payloads. In view of the specific and narrowly defined operational and mission objectives around which this known launch vehicle was designed, one cannot readily adapt this known, large capacity launch vehicle to carry much lesser weight payloads to typically closer proximity earth orbits, especially low altitude polar earth orbits, for the vehicle and its rocket engines were not designed and constructed to account for these operational parameters.
In another known parallel configuration launch vehicle, nine solid "strap-on" rocket motors are positioned along the circumference of a high output liquid burning first stage core engine. Six of the solid rocket motors, along with the liquid core engine, are ignited at lift-off in order to raise particularly heavy payloads from the ground. Because the solid rocket motors are provided principally to assist in the initial launching of the launch vehicle from the ground, they have a relatively short burn life of on the order of about fifty seconds, after which they are jettisoned from the continuously burning liquid core stage. Following jettisoning of the six "strap-on" motors, the remaining three solid rocket motors are ignited while the vehicle is in flight in order to further augment the thrust output of the continuously burning liquid engine, and are burned to completion and thereafter jettisoned. Thereafter, the launch vehicle operates as a conventional series configuration multistage rocket in the manner set forth above.
In view of the foregoing, it is clear that there exists a need for an expendable launch vehicle which is readily reconfigurable to deliver a variety of different size payloads inexpensively and reliably into a range of earth orbits. Accordingly, it is an object of the present invention to provide a launch vehicle and method of launch vehicle operation for delivering relatively light payloads such as one or more satellites into earth orbit in as reliable and cost-effective a manner as is possible.
Another object of the present invention is to provide a launch vehicle and method of launch vehicle operation which utilizes, to as large an extent as possible, proven launch vehicle components for delivering a payload into earth orbit.
Yet another object of the present invention is to provide a launch vehicle and method of launch vehicle operation which is readily adaptable to carry payloads of a variety of different weights into a range of orbital configurations around the earth.
Yet still another object of the present invention is to provide a launch vehicle and method of launch vehicle operation which includes a plurality of rocket engine stages arranged in a parallel configuration that is adaptable to a wide range of payload capacities for delivery into one of a variety of different earth orbits.
Still yet another object of the present invention is to provide a parallel configuration, multistage launch vehicle and method of launch vehicle operation which provides improved dynamic stability and enhanced vehicle control up to deployment of a payload such as a satellite into earth orbit.
A further object of the present invention is to provide a parallel configuration, multistage launch vehicle and method of launch vehicle operation which eliminates the need for a reaction control system to provide attitude control during operation of the early stages of the launch vehicle.
Yet a further object of the present invention is to provide a parallel configuration, multistage launch vehicle and method of launch vehicle operation which employs for its lower stages substantially similar rocket motors and related equipment to provide a greater degree of commonality of design than has previously been achieved in the aerospace industry.
These and other objects and advantages of the present invention will become apparent from a reading of the detailed description below in conjunction with the accompanying drawings.